The present invention relates to a self-extinguishing thyristor having a built-in reverse conducting diode.
The structure of a GTO (Gate Turn off) thyristor having a built-in reverse conducting diode, i.e., a reverse conducting thyristor device is disclosed in literature such as U.S. Pat. No. 4,943,840 (EP No. 224757B1) or U.S. Pat. No. 4,791,470 (Japanese Patent Laying-Open Gazette No. 61-144065), for example.
FIG. 18 is a plan view of a reverse conducting thyristor device of background art 1. A reverse conducting diode region 101 is arranged on an inner region of a semiconductor substrate and a high-resistance region 102 and a self-extinguishing thyristor region 103 are successively formed on an outer region thereof toward the outer peripheral end of the semiconductor substrate, while part of the outermost peripheral region of the semiconductor substrate is engaged in a concave portion of end field protective rubber 104. An external takeout gate electrode region 105 is provided on an inner portion in the self-extinguishing thyristor region 103. FIG. 19 is a sectional view of the reverse conducting thyristor device of the background art 1, and corresponds to a longitudinal sectional view related to the line A-Axe2x80x2 shown in FIG. 18. A cathode electrode and an anode electrode of the reverse conducting diode region 101 consisting of a P-N-N+ layer are in common with an anode electrode 106 and a cathode electrode 107 of the self-extinguishing thyristor region 103 consisting of a P-N+-N-P-N layer respectively.
FIG. 20 is a plan view of a reverse conducting thyristor device of prior art 2. A reverse conducting diode region 101 is arranged on the innermost region of a semiconductor substrate and a high-resistance region 102 and a self-extinguishing thyristor region 103 are successively formed on its outer side toward the outer peripheral end of this substrate, while end field protective rubber 104 is provided on the outer peripheral end of this substrate. An external takeout gate electrode region 105 is provided on an outer portion of the self-extinguishing thyristor region 103. FIG. 21 is a longitudinal sectional view of the reverse conducting thyristor device of the prior art 2 related to the line A-Axe2x80x2 in FIG. 20. A cathode electrode and an anode electrode of the reverse conducting diode region 101 consisting of a P-N-N+ layer are in common with an anode electrode 106 and a cathode electrode 107 of the self-extinguishing thyristor region 103 consisting of a P-N+-N-P-N layer respectively.
FIG. 22 is a plan view of a reverse conducting thyristor device of background art 3. In this background art 3, a self-extinguishing thyristor region 103 is arranged on the innermost region of a semiconductor substrate and a high-resistance region 102 and a reverse conducting diode region 101 are formed toward an outer region of the semiconductor substrate contrarily to the background and prior art 1 or 2, while the outer peripheral end of this substrate is engaged in a concave portion of end field protective rubber 104. Further, an external takeout gate electrode 105 is provided on an outer portion of the self-extinguishing thyristor region 103. FIG. 23 is a longitudinal sectional view of the reverse conducting thyristor device of the background art 3 related to the line A-Axe2x80x2 in FIG. 22, and both electrodes of a cathode and an anode of the reverse conducting diode region 101 consisting of a P-N-N+ layer are in common with an anode electrode 106 and a cathode electrode 107 of the self-extinguishing thyristor region 103 consisting of a P-N+-N-P-N layer respectively.
i) When comparing loss caused in the reverse conducting diode region 101 and the self-extinguishing thyristor region 103 in a general operation, loss in recovery takes a leading part in the diode while power loss at a turn-on time and a turn-off time takes a leading part in the case of the self-extinguishing thyristor, and hence the self-extinguishing thyristor region 103 causes considerably large loss as compared with the reverse conducting diode region 101.
In the reverse conducting thyristor device having the structure of the background and prior art 1 or 2, therefore, there is such a problem that loss caused in the self-extinguishing 94 thyristor region 103 located on the outer side of the semiconductor substrate in the general operation is large and hence heat generated by this power loss fills the end field protective rubber 104 to deteriorate the characteristics of this rubber 104.
ii) When the external takeout gate electrode region 105 is arranged on the intermediate region of the semiconductor substrate as in the background art 1 or 3, it is necessary to form a takeout terminal portion on a sheath storing the semiconductor substrate for implementing connection of the external takeout gate electrode and the outside through this takeout terminal portion, in order to connect the external takeout gate electrode with the outside. At this time, it is necessary to provide the sheath with a takeout terminal portion having a shape projecting toward the central axis of the semiconductor substrate so that the takeout terminal portion of the sheath is not in contact with the cathode electrode 107 of the self-extinguishing thyristor region 103 in the background art 1 or so that this terminal portion is not in contact with the cathode electrode 107 of the reverse conducting diode region 101 in the case of the background art 3. In the reverse conducting thyristor device having the structure of the background art 1 or 3, therefore, there is such a problem that the structure of the sheath storing the semiconductor substrate is complicated and the sheath becomes high-priced.
Such problems (i) and (ii) are common not only in a GTO thyristor (the case where a gate terminal is lead-shaped) having a built-in reverse conducting diode but also in a device having a GCT (Gate Commutated Turn-off) thyristor whose gate terminal consists of a ring-shaped metal plate and a reverse conducting diode. The structure and the operating principle of the GCT thyristor are disclosed in Japanese Pat. Laying-Open Gazette No. 9-201039 (EPO785627A2).
The present invention has been proposed in order to solve the aforementioned problems (i) and (ii), and aims at providing a reverse conducting thyristor device, a pressure-connection type semiconductor device and a semiconductor substrate in which generated heat resulting from power loss in a self-extinguishing thyristor region will not fill end field protective rubber provided on an outer peripheral end portion of a semiconductor substrate and the structure of a sheath storing the semiconductor substrate can also be simplified at the same time.
A first aspect of the present invention comprises a semiconductor substrate, a self-extinguishing thyristor region, formed in the said semiconductor substrate, structuring a self-extinguishing thyristor comprising a gate part layer, a gate electrode region comprising an upper layer region of the same conductivity type as the said gate part layer, formed in an outer peripheral region of the said semiconductor substrate along the outer periphery of the said semiconductor substrate to enclose the said self-extinguishing thyristor region with an external takeout gate electrode formed on its surface, at least one connecting region, formed in the said semiconductor substrate, comprising a surface region of the same conductivity type as the said gate part layer and connecting the said gate part layer and the said upper layer region with each other through the said surface region, at least one isolation region, formed in the said semiconductor substrate, completely enclosed with the said self-extinguishing thyristor region, the said gate electrode region and the said connecting region, and at least one reverse conducting diode region, formed in the said semiconductor substrate, whose outer peripheral portion is completely enclosed with the said isolation region for structuring a reverse conducting diode, and is characterized in that the said isolation region comprises an isolation structure for electrically isolating the said self-extinguishing thyristor region and the said reverse conducting diode region.
According to the first aspect, the outer peripheral portion of the reverse conducting diode region is entirely enclosed with the isolation region, and the gate part layer and the upper layer region of the gate electrode region can be connected through the connecting region with low resistance. Further, the self-extinguishing thyristor region is arranged on an inner region of the semiconductor substrate, whereby it is possible to inhibit heat resulting from power loss in the self-extinguishing thyristor region from conducting to an end field protective rubber provided on the outermost peripheral region of the semiconductor substrate and filling the same.
A second aspect of the present invention is a reverse conducting thyristor device described in the first aspect, and characterized in that the said connecting region has a plurality of connecting regions, the said isolation region has a plurality of isolation regions, the said reverse conducting diode region also has a plurality of reverse conducting diode regions, each of the said plurality of isolation regions is enclosed with corresponding adjacent ones among the said plurality of connecting regions, the said self-extinguishing thyristor region and the said gate electrode region, and further the outer peripheral portion of each of the said plurality of reverse conducting diode regions is completely enclosed with a corresponding one among the said plurality of isolation regions.
According to the second aspect, the gate part layer is connected with the upper layer region of the gate electrode region on the outermost peripheral side through the plurality of connecting regions, whereby the gate part layer can be connected to the upper layer region with lower resistance.
A third aspect of the present invention is the reverse conducting thyristor device described in the second aspect, and further comprises the said external takeout gate electrode entirely formed on the said surface of the said upper layer region, a gate electrode formed on a surface of the said gate part layer, and a gate wiring pattern formed on a surface of the said surface region of each of the said plurality of connecting regions and connecting the said gate electrode and the said external takeout gate electrode with each other.
According to the third aspect, the gate electrode can be connected with the external takeout gate electrode located along the outer periphery on the outermost peripheral side of the substrate through the gate wiring patterns on the substrate with the same potential. Therefore, connection between the outside and the gate electrode can be readily enabled simply by only contact between the external takeout gate electrode on the outermost peripheral side of the substrate and a takeout portion on a sheath side without performing specific alignment when storing the reverse conducting thyristor device according to this aspect in the sheath. Thus, the structure of the sheath can be simplified.
A fourth aspect of the present invention is the reverse conducting thyristor device described in the third aspect, and characterized in that the respective ones of the said plurality of reverse conducting diode regions line up around a central axis of the said semiconductor substrate along the same cirucmferential direction at equal intervals.
According to the fourth aspect, the plurality of reverse conducting thyristor regions are uniformly divided, whereby stable turn-on and turn-off characteristics can be obtained.
A fifth aspect of the present invention is the reverse conducting thyristor device described in the fourth aspect, and is characterized in that the said self-extinguishing thyristor region corresponds to the innermost region of the said semiconductor substrate including the said central axis of the said semiconductor substrate.
According to the fifth aspect, the self-extinguishing thyristor region is provided on the innermost region in the substrate, whereby influence on the substrate outer peripheral region side by heat generated in this region can be further suppressed.
A sixth aspect of the present invention is the reverse conducting thyristor device described in the first aspect, and characterized in that the said isolation region corresponds to a first isolation region, the said isolation structure corresponds to a first isolation structure, the said reverse conducting diode region corresponds to a first reverse conducting diode region structuring a first reverse conducting diode, and the said reverse conducting thyristor device further comprises a second reverse conducting diode region, structuring a second reverse conducting diode, formed in a region of the said semiconductor substrate inward beyond the said self-extinguishing thyristor region, and a second isolation region formed in a region of the said semiconductor substrate held between the said second reverse conducting diode region and the said self-extinguishing thyristor region and comprising a second isolation structure for electrically isolating the said second reverse conducting diode region and the said self-extinguishing thyristor region.
According to the sixth aspect, an advantage similar to the first aspect is attained also in the case of a structure holding the self-extinguishing thyristor region with the first and second reverse conducting diode regions.
A seventh aspect of the present invention comprises the said reverse conducting thyristor device described in the third aspect, a ring-shaped end field protective member comprising a concave portion formed on its inner peripheral side surface part side so that a part excluding a part formed with the said external takeout gate electrode in the said gate electrode region of the said semiconductor substrate is engaged in the said concave portion, a ring gate whose lower surface is electrically in contact with the said external takeout gate electrode and a gate terminal whose first end portion is electrically in contact with an upper surface of the said ring gate and whose second end portion is extended toward the outside.
According to the seventh aspect, it is possible to prevent the end field protective member from being influenced by heat generated in the self-extinguishing thyristor region while takeout of the gate electrode to the outside can be completed by simply bringing the ring gate into contact with the external takeout gate electrode with no requirement for specific alignment, provision of a specific structure on a sheath of a pressure-connection type semiconductor device is made unnecessary and the sheath can be simplified.
An eighth aspect of the present invention comprises a self-extinguishing thyristor region structuring a self-extinguishing thyristor and comprising a gate part layer, a gate electrode region formed on an outer peripheral region and enclosing the said self-extinguishing thyristor region, a reverse conducting diode region formed as a reverse conducting diode in a region held between the said self-extinguishing thyristor region and the said gate electrode region, first and second connecting means for connecting the said gate part layer and an uppermost layer of the said gate electrode region which is of the same conductivity type as the said gate part layer to the same potential and isolation means for performing isolation between the said reverse conducting diode region and the said gate electrode region, isolation between the said reverse conducting diode region and the said first connecting means, isolation between the said reverse conducting diode region and the said second connecting means and isolation between the said reverse conducting diode region and the said self-extinguishing thyristor region.
According to the eighth aspect, a semiconductor substrate having an advantage similar to the first aspect can be obtained.